Securing and maintaining bones in a preferred alignment may be performed by attaching a plurality of bone anchor subassemblies to one or more bones and subsequently securing the bone anchor subassemblies together in a desired orientation with a bone position retainer, wherein such a bone position retainer includes a "longitudinal member," and in some cases, "connectors" as is known in the art. That is, the longitudinal member connects the bone anchor assemblies together, and (if needed), the connectors are used to secure the bone anchor subassemblies to the longitudinal member. Accordingly, there are at least two criteria that would be desirable to be satisfied when securing bones in a desired alignment using bone anchor subassemblies (also denoted as "bone anchors") and a bone position retainer:
(i) it is desirable to attach each bone anchor to a bone in a manner that will inhibit movement of the anchor relative to the bone. Thus, the orientation of the bone anchor to its attached bone may be dependent on, e.g., the bone configuration, density, and/or fractures therein; PA1 (ii) the bone position retainer must be attached to each bone anchor, and in particular, to an included shaft, in a manner so that the longitudinal member (of the bone position retainer) is oriented to effectively maintain the desired alignment of bones. PA1 (i) Determining a desired orientation of one or more bones of a patient; PA1 (ii) Determining a position of the bone position retainer that will facilitate the desired orientation of the bones; PA1 (iii) Determining an appropriate type and size of bone anchor for securing each bone to the bone position retainer; PA1 (iv) Securing each bone anchor in a preferred position within a bone; and PA1 (v) Securing the bone position retainer to each bone anchor at a desired orientation, wherein for each anchor there is one or more washer pairs (or functional equivalents thereof) for providing mating surfaces that can be tightened together to produce the desired orientation, wherein the friction between the mating surfaces is effective for maintaining the orientation of the bone anchor relative to the bone position retainer.
In order to satisfy the above criteria, it may be preferable that the shafts of the bone anchors are not parallel to each other and/or not perpendicular to the longitudinal member when they are attached to their respective bones. Moreover, for each bone alignment procedure performed using bone anchors and bone position retainers, the orientations of the shafts relative to one another and the longitudinal member may be substantially unique.
Accordingly, a preferable position of the longitudinal member can be compromised by the various orientations of the bone anchoring shafts, these various orientations due to, e.g., the preferred positions of the anchors when they are secured to the bones. Thus, it would be advantageous to have the ability to firmly secure such bone anchoring shafts to a bone position retainer, wherein the shafts may be at various orientations to the longitudinal member.